1. Field of the Invention
The present invention relates to an electromagnetic type fuel injection valve. An associated fuel pump forces fuel into the electromagnetic type fuel injection valve, which permits the injecting of the fuel toward an associated suction tube, which is connected to a gasoline engine.
2. Description of the Prior Art
An electromagnetic type fuel injection valve disclosed in Japanese Utility Model Application Laid-Open No. 3-35256, comprises: a cylindrical housing having a stationary core extending from its bottom toward its opening end; an apertured valve seat piece having a fuel metering-and-injecting aperture, said valve seat piece being fixed to the terminal engagement portion of the housing; a flat valve situated between the lower end of the stationary core and the fuel metering-and-injecting aperture to open and close the aperture; and an electric coil positioned in the annular space defined between the outer circumference of the stationary core and the inner circumference of the housing.
When an electric current is made to flow in the electric coil, the flat valve is magnetically attracted to the lower end of the stationary core, thereby opening the fuel metering-and-injecting aperture.
Then, the pumped fuel flows into the annular space defined between the inner circumference of the housing and the outer circumference of the coil, and then the fuel flows from the annular space to the fuel metering-and-injecting aperture to inject to the suction tube of the gasoline engine.
Thus, a desired amount of fuel flows to the suction tube of the gasoline engine, and then, the remaining amount of fuel in the annular space is allowed to return to the fuel tank via a fuel-return path, which opens on the opposite side of the housing. The fuel injection valve which permits the fuel to flow from the outer circumference of the housing to the annular space inside of the housing is called "Side-Feeding Type".
Advantageously the use of flat valve permits reduction of the longitudinal size of the whole device. Also advantageously, no fuel-feeding through hole is made in the stationary core, thus providing an increased cross area for permitting an increased amount of magnetic flux to pass therethrough. For these reasons side-feeding, electromagnetic type fuel injection valves can be designed to be compact.
As described above, the remaining amount of fuel is made to return from the annular space to the fuel tank via the fuel-return path for reuse after injection. This fuel circulating is continued during the running operation of the gasoline engine.
The returning fuel flows around the outer circumference of the coil so that it may be heated by the heat generated in the coil when an electric current flows therein. As a result the temperature of the returning fuel rises.
Thus, the temperature of the fuel in the fuel tank rises gradually until the fuel vapor appears in the fuel tank. This does not favor the evaporation preventing rule, which prescribes the inhibiting of the releasing of fuel evaporation into the surrounding circumference.
An electromagnetic type fuel injection valve disclosed in Japanese Patent Application Laid-Open No. 61-70166 is called "Fuel Ejection Valve of Top-Feeding Type", in which fuel is made to flow down in the longitudinal fuel channel of the stationary core, and flow along the needle valve, finally injecting from the fuel metering-and-injecting aperture of the valve seat. Thus, a desired amount of fuel flows to the suction tube of the gasoline engine. No fuel is circulated and heated as in the side-feeding type valve, and therefore, the fuel injection valve of "Top-Feeding Type" is free of the temperature rise of the fuel in the fuel tank.
Disadvantageously, this type of fuel injection valve has an increased longitudinal length, thus reducing the freedom with which it can be mounted to the machine. Particularly such a fuel injection valve is difficult to be mounted to a multi-suction type of engine comprising a single cylinder having a plurality of suction valves fixed thereto.